The former is described as the sense of smell, the latter is
part of the common chemical senses, a system designed to
protect birds from the harmful effects of irritants. Stimulation of trigeminal chemoreceptors may serve as a cue for
avoidance (Jakubas and Mason, 1991). Additionally, olfactory cues may serve as conditional stimuli to which learned
food aversions can be formed when paired in the presence
of toxicants or irritants (Clark and Mason, 1987).